The billionaire is ready to take out Florida’s multi-millionaire governor.

In a nationwide push to fight Republicans who deny the existence of man-made climate change, investor-turned-activist Tom Steyer has founded a Florida political committee, seeded it with $750,000 of his own money and says he’ll spend far more to help Democrat Charlie Crist defeat Gov. Rick Scott.

Florida Democrats are buzzing about Steyer spending $10 million, which he won’t discuss. Republicans say the California Democrat is a phony environmentalist, but they nevertheless worry his financial commitment could be real in Florida.

“It’s hard to look at the map of the United States and not understand that not only is Florida Ground Zero for climate [change], it’s the third most-populous state,” Steyer said in a sit-down interview Friday with The Miami Herald.

“When you think about why this is an important state to be in, it’s because it’s actually a linchpin,” Steyer, 57, said, underscoring Florida’s standing as the nation’s biggest swing state.

Of the seven states in which Steyer plans to make waves, Florida is the most expensive in which to campaign. In the coming weeks, Steyer plans to open NextGen Climate Action Florida’s headquarters in Miami, which is one of the nation’s most at-risk cities from rising seas and hurricanes.

NextGen Climate, which has already conducted extensive polling, plans to spend big on field organization efforts to identify and motivate voters. It won’t advertise only on TV, like some elections groups.

Scott, who pumped $75.1 million of his own money into his first 2010 campaign, has spent more than $20 million on TV ads. Crist and Democrats have spent about $5 million. Scott’s political and campaign committees have an $8.1 million cash-on-hand advantage over Crist’s.

All told, spending in Florida could top $150 million, two-thirds of it for Scott.

“If someone spends $10 million, it absolutely could alter the margins in the race,” said David “DJ” Johnson, a top Florida political consultant and former executive director of the Republican Party of Florida.